The present invention relates generally to pharmaceutical preparation and more specifically relates to a method for preparing sucralose.
There are many patented technologies worldwide for preparing sucralose from sucrose. However, product yield is low in general due to numerous defects in the course of preparation. The first defect is that by-products such as sulfur dioxide and the like are not well removed during preparation of a chlorinating agent. These acidic impurities seriously affect the selectivity of chlorination reaction and increase the quantity of oxidation products and carbonation products. As a result, product yield could not be increased. The second defect is that an effective catalyst is not available for increasing reaction selectivity. As a result of numerous experiments over a long period of time, the inventor of the present invention discovered that by adding a mixture of phenolic antioxidant and general phase transfer catalyst mixed according to a certain proportion in a reaction system, selectivity of chlorination reaction could be significantly increased, reaction temperature could be lowered, various side reactions could be reduced and product yield could be increased accordingly. The third defect is that sucralose-6-ester must undergo multiple refining steps during deesterification in order to produce qualified products, therefore product loss is increased and product yield is lowered. In view of the above, the inventor of the present invention extracts less polar impurities by using solvent so as to avoid loss and trouble as a result of multiple refining steps. Preparation of sucralose by using the method according to the present invention could increase product yield to more than 40%.